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.TH EXPAND 1 "Feb 1, 1995"
.SH NAME
expand, unexpand \- expand TAB characters to SPACE characters, and vice versa
.SH SYNOPSIS
.LP
.nf
\fBexpand\fR [\fB-t\fR \fItablist\fR] [\fIfile\fR]...
.fi

.LP
.nf
\fBexpand\fR [\fB-\fItabstop\fR\fR] [\fB-\fItab1,\fR\fR \fItab2,.\fR \fI\&.\fR \fI\&.,\fR \fItabn\fR] [\fIfile\fR]...
.fi

.LP
.nf
\fBunexpand\fR [\fB-a\fR] [\fB-t\fR \fItablist\fR] [\fIfile\fR]...
.fi

.SH DESCRIPTION
.LP
The \fBexpand\fR utility copies \fIfile\fRs (or the standard input) to the
standard output, with TAB characters expanded to SPACE characters. BACKSPACE
characters are preserved into the output and decrement the column count for TAB
calculations. \fBexpand\fR is useful for pre-processing character files (before
sorting, looking at specific columns, and so forth) that contain TAB
characters.
.sp
.LP
\fBunexpand\fR copies \fIfile\fRs (or the standard input) to the standard
output, putting TAB characters back into the data. By default, only leading
SPACE and TAB characters are converted to strings of tabs, but this can be
overridden by the \fB-a\fR option (see the OPTIONS section below).
.SH OPTIONS
.LP
The following options are supported for \fBexpand\fR:
.sp
.ne 2
.na
\fB\fB-t\fR \fItablist\fR \fR
.ad
.RS 26n
Specifies the tab stops. The argument \fItablist\fR must consist of a single
positive decimal integer or multiple positive decimal integers, separated by
blank characters or commas, in ascending order. If a single number is given,
tabs will be set \fItablist\fR column positions apart instead of the default
\fB8\fR. If multiple numbers are given, the tabs will be set at those specific
column positions.
.sp
Each tab-stop position \fIN\fR must be an integer value greater than zero, and
the list must be in strictly ascending order. This is taken to mean that, from
the start of a line of output, tabbing to position \fIN\fR causes the next
character output to be in the (\fIN\fR+1)th column position on that line.
.sp
In the event of \fBexpand\fR having to process a tab character at a position
beyond the last of those specified in a multiple tab-stop list, the tab
character is replaced by a single space character in the output.
.RE

.sp
.ne 2
.na
\fB\fB-\fR\fItabstop\fR \fR
.ad
.RS 26n
Specifies as a single argument, sets TAB characters \fItabstop\fR SPACE
characters apart instead of the default \fB8\fR.
.RE

.sp
.ne 2
.na
\fB\fB-\fR\fItab1\fR\fI,\|tab2,...,tabn\fR \fR
.ad
.RS 26n
Sets TAB characters at the columns specified by
\fB-\fR\fItab1,tab2,...,\|tabn\fR
.RE

.sp
.LP
The following options are supported for \fBunexpand\fR:
.sp
.ne 2
.na
\fB\fB-a\fR \fR
.ad
.RS 15n
Inserts TAB characters when replacing a run of two or more SPACE characters
would produce a smaller output file.
.RE

.sp
.ne 2
.na
\fB\fB-t\fR \fItablist\fR \fR
.ad
.RS 15n
Specifies the tab stops. The option-argument \fItablist\fR must be a single
argument consisting of a single positive decimal integer or multiple positive
decimal integers, separated by blank characters or commas, in ascending order.
If a single number is given, tabs will be set \fItablist\fR column positions
apart instead of the default \fB8\fR. If multiple numbers are given, the tabs
will be set at those specific column positions. Each tab-stop position \fIN\fR
must be an integer value greater than zero, and the list must be in strictly
ascending order. This is taken to mean that, from the start of a line of
output, tabbing to position \fIN\fR will cause the next character output to be
in the (\fIN\fR+1)th column position on that line. When the \fB-t\fR option is
not specified, the default is the equivalent of specifying \fB-t\fR \fB8\fR
(except for the interaction with \fB-a\fR, described below).
.sp
No space-to-tab character conversions occur for characters at positions beyond
the last of those specified in a multiple tab-stop list.
.sp
When \fB-t\fR is specified, the presence or absence of the \fB-a\fR option is
ignored; conversion will not be limited to the processing of leading blank
characters.
.RE

.SH OPERANDS
.LP
The following operand is supported for \fBexpand\fR and \fBunexpand\fR:
.sp
.ne 2
.na
\fB\fB\fIfile\fR\fR \fR
.ad
.RS 9n
The path name of a text file to be used as input.
.RE

.SH ENVIRONMENT VARIABLES
.LP
See \fBenviron\fR(7) for descriptions of the following environment variables
that affect the execution of \fBexpand\fR and \fBunexpand\fR: \fBLANG\fR,
\fBLC_ALL\fR, \fBLC_CTYPE\fR, \fBLC_MESSAGES\fR, and \fBNLSPATH\fR.
.SH EXIT STATUS
.LP
The following exit values are returned:
.sp
.ne 2
.na
\fB\fB0\fR \fR
.ad
.RS 7n
Successful completion
.RE

.sp
.ne 2
.na
\fB\fB>0\fR \fR
.ad
.RS 7n
An error occurred.
.RE

.SH ATTRIBUTES
.LP
See \fBattributes\fR(7) for descriptions of the following attributes:
.sp

.sp
.TS
box;
c | c
l | l .
ATTRIBUTE TYPE	ATTRIBUTE VALUE
_
CSI	enabled
_
Interface Stability	Standard
.TE

.SH SEE ALSO
.LP
.BR tabs (1),
.BR attributes (7),
.BR environ (7),
.BR standards (7)
